Start-up method and apparatus for continuous casting

ABSTRACT

Start-up apparatus and method for continuous casting apparatus including a relatively large holding or casting vessel having a relatively small casting outlet or channel at the base thereof to which is attached an open ended mold. The mold construction and a starter bar is arranged so that slag which prevents efficient start-up is kept out of the mold. When molten metal is poured into the casting vessel a fusable plug associated with the starter bar holds the molten metal within the vessel until a substantial non-turbulent head of molten metal has formed in the vessel to cause the slag to rise away from the channel leading to the mold. The mold structure includes a restrictive nozzle and a skim chamber ahead of the nozzle which are operative to trap residual slag in the molten metal. A starter bar sleeve feature insures effective sealing to prevent molten metal breakouts during start-up.

[ 1 Nov. 26, 1974 ABSTRACT START-UP METHOD AND APPARATUS FOR CONTINUOUSCASTING [75] Inventors: Ralph R. McNitt, Okemos; Edward J. Fox GrandLedge both of Mich Start-up apparatus and method for continuous castingapparatus including a relatively large holding or cast- Assignee:General Motors Corporation,

ing vessel having a relatively small casting outlet or Dem)",Mlchchannel at the base thereof to which is attached an open ended mold.The mold construction and a starter 22 Filed: Sept. 27, 1973 21 App].No.: 401,436

bar is arranged so that s'lag which prevents efficient start-up is keptout of the mold. When molten metal is poured into the casting vessel afusable plug associated. with the starter bar holds the molten metalwithin the vessel until a substantial non-turbulent head of molten metalhas formed in the vessel to cause the 482 mm HUN 6 m 2 "4 H6 mmh 6 .r""3 e "."S I M C d std U.mF. 111 2 2 00 555 [rl.|.

slag to rise away from the channel leading to the mold. [561 ReferencesCited The mold structure includes a restrictive nozzle and a UNITEDSTATES PATENTS skim chamber ahead of the nozzle which are operative totrap residual slag in the molten metal. A starter bar sleeve featureinsures effective sealing to prevent molten metal breakouts duringstart-up.

2,707,813 5/1955 164/85 X 3,286,309 11/1966 Brondyke.......,. 164/281 XFOREIGN PATENTS OR APPLICATIONS 1,235,374 6/1971 GreatBritain...................... 164/281 6 Claims, 5 Drawing FiguresPrimary ExaminerAndrew R. Juhasz Assistant Examiner-John S. BrownAttorney, Agent, or FirmPeter P. Kozak Pmtmmnv'zslsn SHEET 2 OF 2START-UP METHOD AND APPARATUS FOR CONTINUOUS CASTING BACKGROUND OF THEINVENTION This invention relates to the continuous casting of metals andmore particularly to start-up apparatus and procedures therefor.

The US. Pat. Nos. 3,731,728; 3,730,251 and 3,726,333, assigned to theassignee of this invention, describe the continuous casting process andapparatus to which the present invention particularly pertains whichincludes a relatively large stationary casting vessel having an outletopening at the base thereof and an open ended mold connected to theoutlet opening. Molten metal is periodically poured into the vessel andthe molten metal is at least partially solidified into a self-sustainingbar within the mold as the metal passes therethrough.

The mold includes a restricted nozzle portion adjacent the vessel outletopening which leads to a primary solidification portion of substantiallygreater internal dimension which in turn leads to a furthersolidification portion of similar dimensions. In the operation of theprocess, the molten metal flows by gravity from the vessel through thevessel outlet opening and through the nozzle into the opened mold. Themetal temperature in the vessel and nozzle is maintained sufficientlyhigh to avoid any metal solidification therein. As the metal flows intothe primary solidification portion, metal solidification begins at thejunction of the nozzle and the primary solidification portion andproceeds as a thin skin layer downstream. At fixed regular timeintervals a predetermined length or segment of the skin layer is pulledforward into the downstream portions of the mold. During theintermediate or dwell period the new skin layer segment which hassolidified in the primary solidification portion during the pull periodor extraction stroke welds on to the preceding segment.

At the start of the pull or extraction stroke the solidifying skinseparates from the nozzle to which it is nonadherent at the junction ofthe nozzle and the primary solidification portion. Liquid steel thenflows in behind the skin as it travels down the mold and new skin formsagainst the nozzle at the said junction, the metal primarysolidification zone, and end of the preceding skin segment.

The new skin lying against the nozzle is stationary and that new skinsolidifying from the end of the withdrawing skin is not. At the end ofthe extraction stroke a dwell of :12 to 0.20 seconds and a slight pushback of the advanced skin is provided for the purpose of providing timeand interface contact between these new skins. During this interval aweld of the skins and additional solidification on the inner surfaceoccurs. At the beginning of the next extraction stroke the solidifiedand welded skin again separates from the nozzle and the cycle repeats.This solidification mechanism continues and further solidificationresults in a selfsustaining continuous bar.

Successful operation of the method requires that the integrity of theinitial skin layer formed in the primary solidification zone bemaintained. Small slag or refractory particles from the vessel liningsmay cause the skin layer to rupture and hence the molten metal to breakthrough the skin layer and to run out of the mold. Since considerableslag is associated with metal initially poured into the vessel, thestart-up of the casting method involves considerable problems.

SUMMARY OF THE INVENTION This invention provides apparatus meansassociated with a starter bar, the mold and the casting vessel tosubstantially eliminate the presence of slag in the mold during start-upand thereafter during casting and to prevent molten metal leakage aboutthe starter bar whereby an efficient start-up is effected. Morespecifically, the starter bar is provided with a fusable plug meansadapted for snug insertion in the vessel outlet opening to prevent theentry of molten metal into the mold for a predetermined time sufficientto permit the casting vessel to be filled with the molten metal to asufficient height to enable the slag poured into the vessel to rise tothe top of the molten metal charge away from the channel leading to themold. Another feature of the invention is the provision of slag trap orskimmer ahead of the mold to prevent residual slag from entering themold after the fusable plug has been melted to permit entry of themolten metal to the mold. The starter bar also includes a sleeve meansfor preventing molten metal run-out or leakage during start-up.

Other features and advantages of the invention will be apparent from thefollowing description with reference to the accompanying drawingswherein:

FIG, 1 is a fragmentary cross-sectional view of a continuous castingvessel and associated mold containing a starter bar in operativeposition shown in elevation;

FIG. 2 is a fragmentary enlargement of FIG. 1 with the starter bar shownin cross-section illustrating the method and apparatus of the inventionabout 4 seconds after the beginning of start-up;

FIG. 3 is similar to FIG. 2 illustrating the method and apparatus about12 seconds after start-up begins;

FIG. 4 is similar to FIG. 2 illustrating the method and apparatus of theinvention about 16 seconds after startup begins; and

FIG. 5 is similar to FIG. 2 illustrating the method and apparatus of theinvention after three extraction strokes.

As previously indicated, the continuous casting method and apparatusinvolved in this invention is disclosed in the aforementioned patents.

Referring to FIGS. 1 and 2, the method and apparatus includes arelatively large refractory vessel 10 having a downwardly extendingchannel 12 leading to a horizontally disposed channel portion 13 and themolten metal outlet 14 located in a recess 16 of the vessel. The outlet14 is surrounded by a-frusto-conical refractory channel block 18cemented in the recess 16 which provides the outlet with a smooth radialface 20. The channels 12 and 13 are preferably of the same generalcross-sectional configuration as outlet opening 14 but of substantiallylarger dimension.

The apparatus further includes a detachable open ended mold assembly 22having a substantially symmetrical cross-sectional configuration alongthe longitudinal axis thereof, comprising sequentially a refractoryspacer ring 24, a restricted internal dimension nozzle 26, a primarymetal solidification portion 28 and a subsequent metal solidificationportion 30. The drawings show apparatus for casting cylindrical bars sothat the block 18, the spacer ring 24, the nozzle 26, and thesolidification portions 28 and 30 are shown to have cylindrical internaldimensions. These dimensions may have rectangular, triangular, oval orany other similar dimension to cast desired bars. The metalsolidification portions 28 and 30 are surrounded by a cooling waterjacket 32 including the water inlet conduit 34 and the water outletconduit 36. Cool water enters through the conduit 34, passes through theopenings 35 into the inner annular chamber 33, around the end 37 of thebaffle 39 into the outer annular chamber 41 to the outlet 36. Thechannel block 18 and spacer ring 24 are preferably formed of arefractory material such as zirconia which is resistant to erosion bythe metal to be cast such as steel. The nozzle 26 is preferably formedof a material such as boron nitride which is inert to and nonwettable bymolten steel. The nozzle 26 as well as the refractory channel block 18and the spacer ring 24 are formed of materials having a relatively lowcoefficient of heat conductivity to insure that the molten metal doesnot solidify on the axial surfaces of these portions of the castingapparatus. The primary solidification portion 28 is formed of a highheat conductivity material such as a copper alloy and the subsequentsolidification portion 30 is preferably formed of a suitable metal linedwith graphite. The mold assembly 22 is sealingly attached to castingvessel by means of the annular cement layer 19 interposed between theradial face 20 of the block 18 and the spacer ring 24 and the bolts 21..

As described in the aforementioned patents, metal casting normallyproceeds in the following manner. Molten metal is transferred to thevessel 10 by a suitable transfer ladle and it flows by gravitydownwardly through the channel 12 through the outlet 14 of the channelblock 18 and thence through the nozzle 26 to the mold. Molten metalsolidification begins at the junction 25 of the nozzle 26 and theprimary solidification portion 28. More specifically, solidificationbegins against the radial face of the nozzle at the junction 25.Initially a thin skin of metal is formed in the primary solidificationportion and in accordance with the metod a method of the skin layer ispulled downstream a predetermined amount and permitted to remainstationary during a relatively short dwell period. During this pullperiod fresh molten metal flows through the nozzle 26 into the primarysolidification zone 28 covering the area vacated by the advancedsolidified skin segment and welds to the rear end thereof during thereverse and dwell period. The intermittent pull and dwell cycle isrepeated continuously and eventually the metal solidifies sufficientlyto form a self-sustaining rod as it is pulled from the subsequentsolidification portion 30 by suitable roller means (not shown). Theprimary solidification portion 28 and the subsequent solidificationportion 30 are preferably formed to have a progressively decreasinginternal diameter to compensate for the shrinkage of the bar as itpasses therethrough so that cast metal to mold contact is maintainedsubstantially throughout the sojourn of the casting bar within the moldto maintain efficient heat transfer.

The casting process is commenced with the use of a starter bar assembly38 comprising a hollow shank portion 40 of somewhat smaller diameterthan the internal diameter of the mold which is capped by the insert 42press welded thereto. The starter bar includes a chill ring 44 which issupported on the starter bolt 46 which is threaded into the insert 42 ofthe shank 40. An aluminum kill wire 48 is wrapped about the bolt 46 todeoxidize the initial steel poured which is usually high in oxygencontent. The assembly includes a starter sleeve 50 having graphite sealrings 52 in the form of a tape wrapped around the sleeve which isseparately inserted into the primary solidification portion 28 and isadapted to fit tightly and sealingly therein due to the graphite seals52. The outer diameter of the sleeve 50 is approximately 0.140 inchsmaller than the inner diameter of the primary solidification portion28in the cold state to enable it to pass through the reduced diameter ofthe secondary mold portion 30. The starter bar assembly furtherincludesa fusable plug 54 supported by the rod 56 screwed into the bolt 46. Whenthe starter bar assembly is in the assembled or operative condition thechill ring 44 is slidably received in the reduced diameter portion 51 ofthe sleeve 50.

As previously stated, the primary solidification portion 28 and thesubsequent solidification portion 30 are preferably formed to have aprogressively decreasing internal diameter. Since the starter sleevetaped diameter 52 is typically of a larger diameter than the exit end ofthe mold assembly, it is inserted separately within the primarysolidification portion from the inlet side thereof during assembly ofthe mold.'The primary and subsequent solidification portions 28 and 30respectively of the mold are typically in the form of a unit. After thestarter sleeve has been inserted within the primary solidification zonethe nozzle 26 is next preferably press fitted therein. Thereafter thespacer ring 24 is assembled adjacent the nozzle 26 which is then clampedto the mold housing by means of the ring 58 bolted to mold housing bybolts (not shown). The mold is then bolted to the vessel with a ring ofsealing compound 19 being interposed between the channel block 18 andthe refractory spacer 24.

Before the molten steel can be cast the vessel 10 and mold assembly arepreheated to thoroughly dehydrate their internal surfaces. Hot gases andflames from a gas fired torch is applied to vessel internal surfacessufficiently to raise them to a temperatureabout 2,200 F. Part of theheating gases exhaust through the open end of the mold. Water is causedto flow through the water jacket 32 so as to maintain the watertemperature leaving the water jacket at about 170 F. Under theseconditions mold internal surfaces are above the boiling point. Thisresults in complete dehydration which is highly desirable since anywater remaining in the mold cavity will flash into steam on coming intocontact with the molten steel, and cause excessive porosity which maydisrupt initial solidification to such an extent that the start-up isunsuccessful.

The starter bar is then inserted into the mold assembly through thedownstream end. When the starter bar is fully inserted the fusable plug54 closes the opening 14 in the channel block 18 with the frusto-conicalportions thereof extending into the channel and the frustoconical flange53 of the chill ring 44 engages the starter sleeve 50 to support it inplace centrally of the mold and positioned longitudinally so that theextreme end 60 of the starter sleeve 50 is in engagement with the nozzle26. The plug 54 has the frusto-conical end which facilitates its entryinto the opening 14. A slope of about 15 to the longitudinal axis issatisfactory for the frusto-conical portion.

The spacer ring 24 has substantially greater internal diameter ordimension than the channel block 18 or the nozzle 26 to provide anannular slag trap or skimmer 66 therebetween. The nozzle 26 must, ofcourse, have an internal diameter large enough to permit the passage ofthe fusable plug 54 therethrough. In consequence of the preheating stepdescribed above, the plug heats up to about l,500 F just before themolten steel is poured into the vessel 10.

FIG. 1 shows the fusable plug 54 and the starter sleeve 50 within themold in a proper position at startup. Molten steel heated to asuperheated temperature of about 3,000 F is initially poured into thevessel 10. FIG. 2 illustrates the apparatus about 4 seconds after thepour has begun. The molten steel 62 with a slag overlay 64 flows intothe channel 12 and extends into partial contact with the fusable plug54. At this time the temperature of the moltensteel is about 2,800 F andthe temperature of the fusable plug is about 2,700 F. The heat contentof the fluid slag and the relatively low temperature of the steelinitially poured into this vessel is insufficient to melt the plug.

FIG. 3 illustrates the system about 12 seconds after the beginning ofthe pour. The molten steel now covers the fusable plug completely andparticles of slag 65 float upward away from the channel outlet opening14. The downward slope of the channel 12 and its smooth contourfacilitates the upward drift of the slag particles from the horizontalchannel portion 13 as shown in FIG. 3. The turbulence and convectionalcurrents within the flowing steel will continue to bring heat into thearea of the fusable plug 54. Fusion of the plug typically occurs afterabout 12 seconds or more depending on the temperature of the steel,temperature of the preheated refractory of the vessel, the refractorycontour, the rate of pour and the amount of slag present. Since thelower portions of the fusable plug are heated first the lower portionsare melted away initially as shown in FIG. 3 permitting molten metal-tobegin flowing into the channel block opening 14. The remainder of theplug fuses shortly thereafter. Meanwhile, particles 65 are caused torise rather than flow into the channel block opening.

FIG. 4 illusrates the system about 16 seconds after the start-up hasbegun. The fusable plug has now melted completely away and residual slag68 has been trapped in the skimmer or slag trap 66. As the molten metalenters the primary solidification portion 28, it is retained initiallywithin the sleeve 50. The graphite ring seal 52 prevents the moltenmetal from leaking past the starter sleeve and the slidable connectionbetween the chill ring 54 and the starter sleeve 50 is sufficientlytight to prevent the flow of the molten metal therethrough. Further, thechilling effect of the chill 44 causes solidification of any moltenmetal flowing through this slide connection. At this point, metal issolidifying on the inner surface of the starter sleeve 50, end of thechill ring 54, onto the head of the starter bolt 46, and the heat of themetal has caused the thin lip 60 of the starter sleeve 50 to approach orexceed the melting point. Nearly all of the fusable plug assembly hasmelted, and the aluminum kill wire 48 is reacting with oxygen present toprevent formation of carbon monoxide, which would interfere with initialsolidification. This heat causes increases in temperature at thethermocouple 27, which through suitable electronic control initiates thefirst pull or extraction stroke; or, at the operators option, he maymanually initiate that stroke. As the starter sleeve withdraws metalflows in behind and solidifies against the inner surface of the primarymodule 28 and against the radial face of the nozzle 26. The graphitetape 52 prevents overlapping of the molten steel between the outerdiameter of the starter sleeve 50 and the inner diameter of the primarymodule 28, as is required to prevent scoring of these components duringstart-up. After the above-mentioned initial stroke, pull and dwellcontinues in a prescribed sequence and progressively increasing rateuntil full extraction conditions are achieved. Through the first severalstrokes, the temperature indicated by the thermo couple progressivelyincreases to, and maintains at the steady state temperature of normalextraction. Sensitivity of this thermocouple is such that. it willindicate a slight temperature variation between the pull and dwell.

FIG. 5 illustrates the apparatus after three extraction strokes anddwell periods. The steel has previously solidified about the chill ring44 and the bolt 46 and also against the internal surfaces of the sleeve50. The molten metal has also solidified as a skin layer consisting ofthe three segments 72, 73 and 74 respectively which were initiated atthe junction 25 at the ridges 75, 76 and 77 respectively and welded toone another at these ridges during the dwell periods.

In accordance with the casting method the intermittent extraction anddwell cycle is continued indefinitely with the casting vessel 10 beingreplenished periodically with sufficient frequency to maintain asubstantial head of molten steel in the vessel 10 and hence to avoid theflow of slag into the channel area during normal casting.

Although the apparatus of this invention has been described in terms ofa cylindrical bar it should be understood that the invention isapplicable to molds of various shapes and sizes including rectangles,ovals, triangles and other polygonal shapes. Also, while the inventionhas been described in terms of certain specific embodiments, other formsmay be adopted within the scope of this invention.

What is claimed is:

1. Continuous casting apparatus and a starting bar therefor comprising:

a holding vessel having an opening at the base thereof,

a detachable open ended mold assembly attached to said vessel about saidopening in fluid flow relation, said assembly including (a) a refractoryspacer ring disposed adjacent said opening in sealing relation theretoand having a substantially greater internal dimension than said opening;(b) a refractory nozzle having an internal dimension substantially lessthan said spacer ring and at least as large as said opening; (c) aprimary solidification chill mold positioned in snug contact with saidnozzle having an internal dimension substantially greater than saidnozzle and forming a shoulder at the junction thereof; (d) a furthersolidification mold portion adjacent said primary mold portion, saidmold portions having progressively diminishing internal dimensions in adirection away from said vessel opening, and

a starter bar means including (a) a sleeve portion adapted for separateinsertion into said primary mold portion having one larger dimensionedend thereof adapted in its operative position for engagement with saidnozzle shoulder and for sealing engagement with said primary moldportion; (b) an elongated bar portion adapted for insertion into thesaid mold through the outlet end thereof to a fully inserted positionincluding a fusable plug end portion adapted for snug insertion intosaid vessel opening in said fully inserted position; a chill portionreceivable within at least a portion of said sleeve operative to locateand support said sleeve in its operative position and (d) an enlargedportion located within said sleeve in the said fully inserted position,said enlarged portion, said chill portion and said sleeve cooperativelyforming a cavity for receiving molten metal and a mechanical grip forholding solidified metal.

2. Continuous casting apparatus and a starting bar therefor comprising:

a holding vessel having a horizontally disposed channel at the basethereof terminating in an outlet opening and a refractory block at saidopening having an internal passage therethrough having a dimensionsubstantially less than the dimension of said channel,

a detachable open ended mold assembly attached to said vessel about saidblock in fluid flow relation, said assembly including (a) a refractoryspacer ring disposed adjacent said block in sealing relation thereto andhaving a substantially greater internal dimension than said block; (b) arefractory nozzle having an internal dimension substantially less thansaid spacer ring and at least as large as said block; (c) a primarysolidification chill mold positioned in snug contact with said nozzlehaving an internal dimension substantially greater than said nozzle andforming a shoulder at the junction thereof; ((1) a furthersolidification mold portion adjacent said primary mold portion, saidmold portions having progressively diminishing internal dimensions in adirection away from said vessel opening, and starter bar means including(a) a sleeve portion adapted for separate insertion into said primarymold portion having one larger dimensioned end thereof adapted in itsoperative position for engagement with said nozzle shoulder and forsealing engagement with said primary mold portion; (b) an elongated barportion adapted for insertion into the said mold through the outlet endthereof to a fully inserted position including a hollow fusable plug endportion adapted for snug insertion into said block passage in said fullyinserted position; (c) a chill portion receivable within at least aportion of said sleeve operative to locate and support said sleeve inits operative position and (d) an enlarged portion located within saidsleeve in the said fully inserted position, said enlarged portion, saidchill portion and said sleeve cooperatively forming a cavity forreceiving molten metal and a mechanical grip for holding solidifiedmetal.

3. Continuous casting apparatus and a starting bar therefor comprising:

a holding vessel having a horizontally disposed channel at the basethereof terminating in an outlet opening and a refractory block at saidopening having an internal passage therethrough having a dimensionsubstantially less than the dimension of said channel,

a detachable open ended mold assembly attached to said vessel about saidopening in fluid flow relation, said assembly including (a) a refractoryspacer ring disposed adjacent said opening in sealing relation theretoand having a substantially greater internal dimension than said opening;(b) a refractory nozzle having an internal dimension substantially lessthan said spacer ring and at least as large as said opening, said block,said spacer ring and said nozzle forming a chamber therebetween; (c) aprimary solidification chill mold positioned in snug contact with saidnozzle having an internal dimension substantially greater than saidnozzle and forming a shoulder at the junction thereof; ((1) a furthersolidification mold portion adjacent said primary mold portion,said moldportions having progressively diminishing internal dimensions in adirection away from said vessel opening, and

starter bar means including (a) a sleeve portion adapted for separateinsertion into said primary mold portion having one larger dimensionedend thereof adapted in its operative position for engagement with saidnozzle shoulder and for sealing engagement with said primary moldportion; (b) an elongated bar portion adapted for insertion into thesaid mold through the outlet end thereof to a fully inserted positionincluding a hollow fusable plug end portion adapted for snug insertioninto said vessel opening in said fully inserted position; (c) a chillportion receivable within at least a portion of said sleeve operative tolocate and support said sleeve in its operative position and (.d) anenlarged portion located within said sleeve in the said fully insertedposition, said enlarged portion, said chill portion and said sleevecooperatively. forming a cavity for receiving molten metal and amechanical grip for holding solidified metal,

said fusable plug being of a thickness so as to resist fusion by moltenmetal poured into contact therewith for a relatively short predeterminedtime necessary for slag contained in the molten metal to rise above saidblock passage and then fuse to permit the molten metal to pass into saidmold assembly, said sleeve one end being relatively thin and fusable incontact with said molten metal.

4. A method for starting a continuous casting process which involvesapparatus comprising a holding vessel having an outlet opening at thebase thereof, a detachable open ended mold assembly attached to saidvessel about said opening in fluid flow relation, said assemblyincluding (a) a refractory spacer ring disposed adjacent said opening insealing relation thereto and having a substantially greater internaldimension than said opening; (b) a refractory nozzle having an internaldimension substantially less than said spacer ring and at least as largeas said opening whereby an annular chamber is formed between saidvessel, said spacer ring and said nozzle; (0) a primary solidificationchill mold portion positioned in snug contact with said nozzle having aninternal dimension substantially greater than said nozzle and forming ashoulder at the junction thereof; (d) a further solidification moldportion adjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of:

inserting a metal sleeve portion into said primary mold portion, saidsleeve being adapted in its operative position for providing sealingengagement with said primary mold portion,

inserting an elongated bar portion into said mold through the outlet endthereof to a fully inserted position, said bar portion including a fixedhollow fusable plug inserted into said vessel opening, said bar portionfurther including a fixed chill portion engaging at least a portion ofsaid sleeve in said fully inserted position, locating and supportingsaid sleeve in its said operative position, said bar portion alsoincluding an enlarged portion within said sleeve in said fully insertedposition, said enlarged portion and said chill portion and said sleeveoperatively forming a cavity for receiving molten metal and providing amechanical grip for holding solidified metal, I

pouring molten metal into said vessel with said plug being operative tohold back the molten metal from entering the mold until the slag hassubstantially risen above said opening,

continuing pouring molten metal into said vessel with said plug beingfused to permit the flow of molten metal through said nozzle into saidsleeve within said primary mold, said molten metal contacting saidsleeve, chill portion and said enlarged portion, said molten metalcontacting said primary mold portion at the junction of said nozzle andsaid primary mold and progressively solidifying within said primary moldand said chill portion,

pulling said starter bar a predetermined length whereby a new skin layerof molten metalsolidifies on the exposed surfaces of the primary mold,permitting the starter bar to dwell a sufficient time to permit the newsegment of metal to weld to the segment previously pulled forward andcontinuing an intermittent pull and dwell cycle.

5. A method for starting a continuous casting process which involvesapparatus comprising a holding vessel having an outlet opening at thebase thereof, a detachable open ended mold assembly attached to saidvessel about said opening in fluid flow relation, said assemblyincluding (a) a refractory spacer ring disposed adjacent said opening insealing relation thereto and having a substantially greater internaldimension than said opening; (b) a refractory nozzle having an internaldimension substantially less than said spacer ring and at least as largeas said opening whereby an annular chamber is formed between saidvessel, said spacer ring and said nozzle; a primary solidification chillmold portion positioned in snug contact with said nozzle having aninternal dimension substantially greater than said nozzle and forming ashoulder at the junction thereof; ((1) a further solidification moldportion adjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of:

separately inserting a metal sleeve portion into said primary moldportion of larger dimension than the other end and being relativelythin, said sleeve being adapted in its operative position for engagementwith said nozzle shoulder and seal ring thereon for providing sealingengagement with said primary mold portion,

inserting an elongated bar portion into said mold through the outlet endthereof to a fully inserted position, said bar portion including a fixedhollow fusable plug inserted into said vessel opening, said bar portionfurther including a fixed chill portion engaging at least a portion ofsaid sleeve in said fully inserted position, locating and supportingsaid sleeve in its said operative position, said bar portion alsoincluding an enlarged portion within said sleeve in said fully insertedposition, said enlarged portion and said chill portion and said sleeveoperatively forming a cavity for receiving molten metal and providing amechanical grip for holding solidified metal,

pouring molten metal into said vessel with said plug being operative tohold back the molten metal from entering the mold until the slag hassubstantially risen above said opening,

continuing pouring molten metal into saidvessel with said plug beingfused to permit the flow of molten metal through said nozzle into saidsleeve within said primary mold, said molten metal contacting saidsleeve, chill portion and said enlarged portion, 7

said molten metal contacting said primary mold portion at the junctionof said nozzle and said primary mold and progressively solidifyingwithin said primary mold and said chill portion,

pulling said starter bar a predetermined length whereby a new skin layerof molten metal solidifies on the exposed surfaces of the primary mold,permitting the starter bar to dwell a sufficient time to permit the newsegment of metal to weld to the segment previously pulled forward andcontinuing an intermittent pull and dwell cycle.

'6. A method for starting a continuous casting process which involvesapparatus comprising a holding vessel having an outlet opening at thebase thereof, a detachable open ended mold assembly attached to saidvessel about said opening in fluid flow relation, said assemblyincluding (a) a refractory spacer ring disposed adjacent said opening insealing relation thereto and having a substantially greater internaldimension than said opening; (b) a refractory nozzle having an internaldimension substantially less than said spacer ringand at least as largeas said opening whereby an annular chamber is formed between saidvessel, said spacer ring and said nozzle; (0) a primary solidificationchill mold portion positioned in snug contact with said nozzle having aninternal dimension substantially greater than said nozzle and forming ashoulder at the junction thereof; (d) a further solidification moldportion adjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of:

separately inserting a metal sleeve portion into said primary moldportion, said sleeve portion having one end of larger dimension than theother end and being relatively thin, said sleeve being adapted in itsoperative position for engagement with said nozzle shoulder and sealring thereon for providing sealing engagement with said primary moldportion,

inserting an elongated bar portion into said mold through the outlet endthereof to a fully inserted position, said bar portion including a fixedhollow fusable plug inserted into said vessel opening, said bar portionfurther including a fixed chill portion engaging at least a portion ofsaid sleeve in said fully inserted position, locating and supportingsaid sleeve in its said operative position, said bar portion alsoincluding an enlarged portion within said sleeve in said fully insertedposition, said enlarged portion and said chill portion and said sleeveoperatively forming a cavity for receiving molten metal and providing amechanical grip for holding solidified metal,

pouring molten metal into said vessel with said plug being operative tohold back the molten metal from entering the mold until the slag hassubstantially risen above said opening,

continuing pouring molten metal into said vessel with and said primarymold and progressively solidifying within said primary mold and saidchill portion, so

that a partially solidified bar is formed which is mechanically grippedbetween said sleeve and said enlarged portion, said sleeve beingoperative to retain said molten metal sufficiently to permit itswithdrawal from said mold through the outlet end of said mold,

pulling said starter bar a predetermined length whereby a new skin layerof molten metal solidifies on the exposed surfaces of the primary mold,permitting the starter bar to dwell a sufficient time to permit the newsegment of metal to weld to the segment previously pulled forward andcontinuing an intermittent pull and dwell cycle.

UNITED STATES PATENT AND TRADEMARK OFFICE QEBTIFICATE OF CORRECTIONPATENT NO. I 3 850 225 DATED November 26, 1974 v 0 (5) Ralph R. McNitt,Edward J. Fox

It is certified that error appears in the above-identified patent andthat said Letters Patent 9 are hereby corrected as shown below:

Column 3, line 40, "metod" should read method Column 3, line 41,"method" should read segment Signed and Scaled this eighteenth D8) 0fMay 1976 [sent Arrest:

RUTH c. msohi -rs. MARSHALL DANN Arresting Officer (ummissium'rnj'larenrs and Trademarks I

1. Continuous casting apparatus and a starting bar therefor comprising:a holding vessel having an opening at the base thereof, a detachableopen ended mold assembly attached to said vessel about said opening influid flow relation, said assembly including (a) a refractory spacerring disposed adjacent said opening in sealing relation thereto andhaving a substantially greater internal dimension than said opening; (b)a refractory nozzle having an internal dimension substantially less thansaid spacer ring and at least as large as said opening; (c) a primarysolidification chill mold positioned in snug contact with said nozzlehaving an internal dimension substantially greater than said nozzle andforming a shoulder at the junction thereof; (d) a further solidificationmold portion adjacent said primary mold portion, said mold portionshaving progressively diminishing internal dimensions in a direction awayfrom said vessel opening, and a starter bar means including (a) a sleeveportion adapted for separate insertion into said primary mold portionhaving one larger dimensioned end thereof adapted in its operativeposition for engagement with said nozzle shoulder and for sealingengagement with said primary mold portion; (b) an elongated bar portionadapted for insertion into the said mold through the outlet end thereofto a fully inserted position including a fusable plug end portionadapted for snug insertion into said vessel opening in said fullyinserted position; (c) a chill portion receivable within at least aportion of said sleeve operative to locate and support said sleeve inits operative position and (d) an enlarged portion located within saidsleeve in the said fully inserted position, said enlarged portion, saidchill portion and said sleeve cooperatively forming a cavity forreceiving molten metal and a mechanical grip for holding solidifiedmetal.
 2. Continuous casting apparatus and a starting bar thereforcomprising: a holding vessel having a horizontally disposed channel atthe base thereof terminating in an outlet opening and a refractory blockat said opening having an internal passage therethrough having adimension substantially less than the dimension of said channel, adetachable open ended mold assembly attached to said vessel about saidblock in fluid flow relation, said assembly including (a) a refractoryspacer ring disposed adjacent said block in sealing relation thereto andhaving a substantially greater internal dimension than said block; (b) arefractory nozzle having an internal dimension substantially less thansaid spacer ring and at least as large as said block; (c) a primarysolidification chill mold positioned in snug contact with said nozzlehaving an internal dimension substantially greater than said nozzle andforming a shoulder at the junction thereof; (d) a further solidificationmold portion adjacent said primary mold portion, said mold portionshaving progressively diminishing internal dimensions in a direction awayfRom said vessel opening, and a starter bar means including (a) a sleeveportion adapted for separate insertion into said primary mold portionhaving one larger dimensioned end thereof adapted in its operativeposition for engagement with said nozzle shoulder and for sealingengagement with said primary mold portion; (b) an elongated bar portionadapted for insertion into the said mold through the outlet end thereofto a fully inserted position including a hollow fusable plug end portionadapted for snug insertion into said block passage in said fullyinserted position; (c) a chill portion receivable within at least aportion of said sleeve operative to locate and support said sleeve inits operative position and (d) an enlarged portion located within saidsleeve in the said fully inserted position, said enlarged portion, saidchill portion and said sleeve cooperatively forming a cavity forreceiving molten metal and a mechanical grip for holding solidifiedmetal.
 3. Continuous casting apparatus and a starting bar thereforcomprising: a holding vessel having a horizontally disposed channel atthe base thereof terminating in an outlet opening and a refractory blockat said opening having an internal passage therethrough having adimension substantially less than the dimension of said channel, adetachable open ended mold assembly attached to said vessel about saidopening in fluid flow relation, said assembly including (a) a refractoryspacer ring disposed adjacent said opening in sealing relation theretoand having a substantially greater internal dimension than said opening;(b) a refractory nozzle having an internal dimension substantially lessthan said spacer ring and at least as large as said opening, said block,said spacer ring and said nozzle forming a chamber therebetween; (c) aprimary solidification chill mold positioned in snug contact with saidnozzle having an internal dimension substantially greater than saidnozzle and forming a shoulder at the junction thereof; (d) a furthersolidification mold portion adjacent said primary mold portion, saidmold portions having progressively diminishing internal dimensions in adirection away from said vessel opening, and a starter bar meansincluding (a) a sleeve portion adapted for separate insertion into saidprimary mold portion having one larger dimensioned end thereof adaptedin its operative position for engagement with said nozzle shoulder andfor sealing engagement with said primary mold portion; (b) an elongatedbar portion adapted for insertion into the said mold through the outletend thereof to a fully inserted position including a hollow fusable plugend portion adapted for snug insertion into said vessel opening in saidfully inserted position; (c) a chill portion receivable within at leasta portion of said sleeve operative to locate and support said sleeve inits operative position and (d) an enlarged portion located within saidsleeve in the said fully inserted position, said enlarged portion, saidchill portion and said sleeve cooperatively forming a cavity forreceiving molten metal and a mechanical grip for holding solidifiedmetal, said fusable plug being of a thickness so as to resist fusion bymolten metal poured into contact therewith for a relatively shortpredetermined time necessary for slag contained in the molten metal torise above said block passage and then fuse to permit the molten metalto pass into said mold assembly, said sleeve one end being relativelythin and fusable in contact with said molten metal.
 4. A method forstarting a continuous casting process which involves apparatuscomprising a holding vessel having an outlet opening at the basethereof, a detachable open ended mold assembly attached to said vesselabout said opening in fluid flow relation, said assembly including (a) arefractory spacer ring disposed adjacent said opening in sealingrelation thereto and having a substantially greater internal dimensionthan said opening; (b) a refraCtory nozzle having an internal dimensionsubstantially less than said spacer ring and at least as large as saidopening whereby an annular chamber is formed between said vessel, saidspacer ring and said nozzle; (c) a primary solidification chill moldportion positioned in snug contact with said nozzle having an internaldimension substantially greater than said nozzle and forming a shoulderat the junction thereof; (d) a further solidification mold portionadjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of: inserting a metal sleeveportion into said primary mold portion, said sleeve being adapted in itsoperative position for providing sealing engagement with said primarymold portion, inserting an elongated bar portion into said mold throughthe outlet end thereof to a fully inserted position, said bar portionincluding a fixed hollow fusable plug inserted into said vessel opening,said bar portion further including a fixed chill portion engaging atleast a portion of said sleeve in said fully inserted position, locatingand supporting said sleeve in its said operative position, said barportion also including an enlarged portion within said sleeve in saidfully inserted position, said enlarged portion and said chill portionand said sleeve operatively forming a cavity for receiving molten metaland providing a mechanical grip for holding solidified metal, pouringmolten metal into said vessel with said plug being operative to holdback the molten metal from entering the mold until the slag hassubstantially risen above said opening, continuing pouring molten metalinto said vessel with said plug being fused to permit the flow of moltenmetal through said nozzle into said sleeve within said primary mold,said molten metal contacting said sleeve, chill portion and saidenlarged portion, said molten metal contacting said primary mold portionat the junction of said nozzle and said primary mold and progressivelysolidifying within said primary mold and said chill portion, pullingsaid starter bar a predetermined length whereby a new skin layer ofmolten metal solidifies on the exposed surfaces of the primary mold,permitting the starter bar to dwell a sufficient time to permit the newsegment of metal to weld to the segment previously pulled forward andcontinuing an intermittent pull and dwell cycle.
 5. A method forstarting a continuous casting process which involves apparatuscomprising a holding vessel having an outlet opening at the basethereof, a detachable open ended mold assembly attached to said vesselabout said opening in fluid flow relation, said assembly including (a) arefractory spacer ring disposed adjacent said opening in sealingrelation thereto and having a substantially greater internal dimensionthan said opening; (b) a refractory nozzle having an internal dimensionsubstantially less than said spacer ring and at least as large as saidopening whereby an annular chamber is formed between said vessel, saidspacer ring and said nozzle; (c) a primary solidification chill moldportion positioned in snug contact with said nozzle having an internaldimension substantially greater than said nozzle and forming a shoulderat the junction thereof; (d) a further solidification mold portionadjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of: separately inserting ametal sleeve portion into said primary mold portion of larger dimensionthan the other end and being relatively thin, said sleeve being adaptedin its operative position for engagement with said nozzle shoulder andseal ring thereon for providing sealing engagement with said primarymold portion, inserting an elongated bar portion into said mold throughthe outlet end thereof to a fully inserted position, said bar portIonincluding a fixed hollow fusable plug inserted into said vessel opening,said bar portion further including a fixed chill portion engaging atleast a portion of said sleeve in said fully inserted position, locatingand supporting said sleeve in its said operative position, said barportion also including an enlarged portion within said sleeve in saidfully inserted position, said enlarged portion and said chill portionand said sleeve operatively forming a cavity for receiving molten metaland providing a mechanical grip for holding solidified metal, pouringmolten metal into said vessel with said plug being operative to holdback the molten metal from entering the mold until the slag hassubstantially risen above said opening, continuing pouring molten metalinto said vessel with said plug being fused to permit the flow of moltenmetal through said nozzle into said sleeve within said primary mold,said molten metal contacting said sleeve, chill portion and saidenlarged portion, said molten metal contacting said primary mold portionat the junction of said nozzle and said primary mold and progressivelysolidifying within said primary mold and said chill portion, pullingsaid starter bar a predetermined length whereby a new skin layer ofmolten metal solidifies on the exposed surfaces of the primary mold,permitting the starter bar to dwell a sufficient time to permit the newsegment of metal to weld to the segment previously pulled forward andcontinuing an intermittent pull and dwell cycle.
 6. A method forstarting a continuous casting process which involves apparatuscomprising a holding vessel having an outlet opening at the basethereof, a detachable open ended mold assembly attached to said vesselabout said opening in fluid flow relation, said assembly including (a) arefractory spacer ring disposed adjacent said opening in sealingrelation thereto and having a substantially greater internal dimensionthan said opening; (b) a refractory nozzle having an internal dimensionsubstantially less than said spacer ring and at least as large as saidopening whereby an annular chamber is formed between said vessel, saidspacer ring and said nozzle; (c) a primary solidification chill moldportion positioned in snug contact with said nozzle having an internaldimension substantially greater than said nozzle and forming a shoulderat the junction thereof; (d) a further solidification mold portionadjacent said primary mold portion, said mold portions havingprogressively diminishing internal dimensions in a direction away fromsaid vessel opening, comprising the steps of: separately inserting ametal sleeve portion into said primary mold portion, said sleeve portionhaving one end of larger dimension than the other end and beingrelatively thin, said sleeve being adapted in its operative position forengagement with said nozzle shoulder and seal ring thereon for providingsealing engagement with said primary mold portion, inserting anelongated bar portion into said mold through the outlet end thereof to afully inserted position, said bar portion including a fixed hollowfusable plug inserted into said vessel opening, said bar portion furtherincluding a fixed chill portion engaging at least a portion of saidsleeve in said fully inserted position, locating and supporting saidsleeve in its said operative position, said bar portion also includingan enlarged portion within said sleeve in said fully inserted position,said enlarged portion and said chill portion and said sleeve operativelyforming a cavity for receiving molten metal and providing a mechanicalgrip for holding solidified metal, pouring molten metal into said vesselwith said plug being operative to hold back the molten metal fromentering the mold until the slag has substantially risen above saidopening, continuing pouring molten metal into said vessel with said plugbeing fused to permit the flow of molten metal through said chamber andsaid nozzle into said sleeve withiN said primary mold, said chamberbeing operative to retain residual slag, said molten metal contactingsaid sleeve, chill portion and said enlarged portion, said molten metalcontacting said primary mold portion at the junction of said nozzle andsaid primary mold and progressively solidifying within said primary moldand said chill portion, so that a partially solidified bar is formedwhich is mechanically gripped between said sleeve and said enlargedportion, said sleeve being operative to retain said molten metalsufficiently to permit its withdrawal from said mold through the outletend of said mold, pulling said starter bar a predetermined lengthwhereby a new skin layer of molten metal solidifies on the exposedsurfaces of the primary mold, permitting the starter bar to dwell asufficient time to permit the new segment of metal to weld to thesegment previously pulled forward and continuing an intermittent pulland dwell cycle.